This study examined motivation to use omni-channel services on mobile devices in fashion stores and the effects of such usage motivation on brand purchase intention through continuous and affective commitment. Data were collected on consumers in their 20s and 30s who experienced omni-channel services during shopping for or purchasing fashion products. An online survey asked 413 consumers to rate their brand purchase intention. Sub-levels of each variable were examined using SPSS 25.0, followed by confirmatory factor analysis using AMOS 19.0. In addition, path analysis using structural equation modeling was applied to analyze associations between variables. The statistical results were mixed. First, only two dimensions of usage motivation for omni-channel services, hedonic and relational motivation, had positive effects on continuous and affective commitment. Second, continuous commitment had a greater effect on purchase intention of brands that provided omni-channel services than it did on affective commitment. Third, of the dimensions of usage motivation, utilitarian motivation had a direct influence on purchase intention in the modified model, while social motivation did not affect service commitment and purchase intention. Finally, our findings suggest that brand loyalty can be built by encouraging service commitments through hedonic and relational motivation, based on the usability of omnichannel services.